For tungsten wires made of tungsten or tungsten alloys, the average width of crystal grains on the surface in the direction perpendicular to the axis of the tungsten wire is below 76nm. The tensile strength of the tungsten wire is above 4800MPa. The diameter is below 100μm.由鎢或是鎢合金所構成之鎢線,在垂直於鎢線之線軸的方向中之表面結晶粒的寬度平均値係在76nm以下,鎢線的抗拉強度係在4800MPa以上,鎢線的線徑係在100μm以下。